Date of Completion

2024

Thesis Type

College of Arts and Science Honors

Department

Biology

First Advisor

Dr. Molly Stanley

Keywords

gustatory receptor neuron, amino acids, combinatorial coding, tastant, umami, tryptone

Abstract

Mammals and insects alike depend on foodstuffs as an essential source of proteins and their constitutive amino acids (AA), several of which cannot be synthesized by the organism. AA consumption by Drosophila melanogaster plays a crucial role in a variety of behaviors that impact the animal’s survival and fitness, including feeding, mating, and egg laying. Underlying neural circuits that dictate such behaviors begin with the activation of distinct subsets of gustatory receptor neurons (GRNs) in the fly labellum, which subsequently transmit taste information to the brain for its integration. However, the mechanisms by which GRNs detect AAs to elicit behavioral responses in Drosophila are not fully characterized. The present study employs behavioral paradigms that evaluate the external and internal mechanisms of tryptone taste detection to describe the roles of three distinct GRN classes within the labellum in AA sensing. Through taste and feeding assays combined with chemogenetics, optogenetics, and chronic neuronal silencing, we describe the canonical roles of the Gr64f-expressing sweet GRNs and Gr66a-expressing bitter GRNs in AA feeding and contrast these circuits to an undescribed, novel set of IR94e-expressing GRNs. This work supports a combinatorial coding paradigm of taste coding in which one chemical ligand activates parallel sensory circuits to expand the range of the sensory experience in the fly.

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